Time division protocol for an ad-hoc, peer-to-peer radio network having coordinating channel access to shared parallel data channels with separate reservation channel

ABSTRACT

A novel protocol for an ad-hoc, peer-to-peer radio network that provides collision-free channel access with an emphasis on improving geographic reuse of the frequency spectrum. The protocol of the invention is executed on the reservation or control channel, and provides a method for allocating data transactions on the data channels. The system of the invention utilizes multiple parallel data channels that are coordinated by a single reservation channel. The transceiver of the system employs two modems to solve the channel reliability issues with multiple channel designs, where one is dedicated as a receive-only modem for gathering channel usage information on the reservation channel. High quality voice, video and data may be transmitted. The reservation channel implements a time division multiple access algorithm with dynamic slot allocation. In a distributed manner, nodes determine geographic reuse of slots based on channel quality extracted from the modem. Signal quality calculations are used to determine the likelihood of a slot reuse causing destructive interference within a node&#39;s neighborhood. Requests for slot usage are compared with the known traffic pattern and accepted or rejected by nodes within RF signal range based on the signal quality calculations.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of co-pending application Ser. No. 09/815,157filed on Mar. 22, 2001.

Priority of provision application Ser. No. 60/246,833, filed on Nov. 8,2000 is herewith claimed.

BACKGROUND OF THE INVENTION

The present invention is directed to a novel protocol for an ad-hoc,peer-to-peer radio network system having coordinating channel access toshared parallel data channels via a separate reservation channel. Thissystem is disclosed in copending application Ser. No. 09/705,588, filedon Nov. 3, 2001, entitled “Methods and Apparatus for CoordinatingChannel Access to Shared Parallel Data Channels”, which application isincorporated by reference herein in its entirety.

The network system having coordinating channel access to shared paralleldata channels via a separate reservation channel of copendingapplication Ser. No. 09/705,588 is directed to a network system, such asradio network, where each node, or radio terminal, of the network iscapable of serving as a node or hop of a routing path of a call fromanother, or to another radio terminal. In that system, communicationbetween nodes or radio terminals is achieved using Carrier SenseMultiple Access with Collision Avoidance (CSMA/CA) protocol with theaddition of multiple parallel data channels serviced by one reservationchannel. By dedicating a separate reservation channel for the multipleparallel data channels, collision-free access by all of the competingnodes or terminals of the service group of the network is greatlyreduced. Communications between terminals or nodes is set up byinformation exchanged on the separate reservation channel, whichinformation includes all of the call set-up information such as datachannel desired to be used for transferring voice, video or data, thedesired power level of at least initial transmission, messaging such asRequest-to-Send (RTS), Clear-to-Send (CTS), Not-Clear-to-Send (NCLS),Acknowledgment (ACK) for indicating reception of the transmitted call,Non-Acknowledgment (NACK) for indicating improper reception of the call,etc. In this system, in order to further ensure fast, adequate andcollision-free transmission and reception, besides a primary modemtypically provided with the transceiver of each node or terminal, asecondary modem is also provided which is dedicated to the reservationchannel when the primary modem of the transceiver is occupied, such aswhen sending out data on a data channel. This system also provides forcollision free transmission and reception between nodes or terminals bytransmitting the reservation and data channels in time slots of timeframes, with the information as to which time slot is to be used beingincluded in the messaging transmitted by the reservation channel. Such aformat not only provides collision-free transmission, but also allowsfor Quality-of-Service (QoS) for different types of Class-of-Service(CoS), Thus, not only may voice and video be transmitted, besides data,but voice and data transmission may be prioritized, so that whencompeting calls vie for a data channel, the delay-dependent voice orvideo transmissions will take precedence. This prioritization isaccomplished by assigning prioritized calls for transmission in earliertime slots of a time frame.

The network system disclosed in U.S. application Ser. No. 09/705,588ensures that every node or terminal of a service set of terminals hasthe most information regarding all of other terminals of that serviceset, so that the choice of data channel to be used, any required delayis transmitting the call, information on power level, and the like, arechecked and updated by each terminal by a practically continuousmonitoring of the reservation channel.

As explained above, the system disclosed in U.S. application Ser. No.09/705,588 utilizes protocol that provides collision-free channelaccess, which also emphasizes improving geographic reuse of thefrequency spectrum.

In U.S. Pat. No. 5,943,322—Mayer, et al., which patent is incorporatedby reference herein, the radio system thereof is for use in battlefieldconditions. The ad-hoc, peer-to-peer radio system of this patent doesnot have, nor require, a base station, as conventional cellular systems,personal communications system (PCC), and the like, require; instead,each radio terminal forming part of the ad-hoc, peer-to-peer radiosystem may alternatively serve as a base station, in addition to beingan ordinary link terminal of the radio system, whereby, if one suchterminal serving as a base station should for some reason becomeinoperative, another terminal may take over and serve as the basestation. In this patent, personal voice communications is based on atime division duplex (TDD) technique in a code division multiple access(CDMA) system, is operated without a fixed base station, and is providedwith simultaneous transmission of a communications channel and a controlchannel, each spread by different PN codes. The PN code facilitatesrestricting communications on the network to a particularvoice-conversation mode and between identified radios. Transmissions areperformed in a time division duplex manner in 62.5 milliseconds slots.One of the radios initiates transmission and maintains power control andtime synchronization normally done by a base station. A network controlstation can voluntarily or by command transfer control of the network toany of the other radios on the network. Colliding transmissions frommore than one radio require the radios to retry transmitting until oneof the radios transmits in an earlier time slot. Conversational modecapability is provided by equipping the radio receivers with despreadersin parallel for permitting a receiving radio to separately despread thesimultaneously transmitted signals all other radios on the network andresponding to each radio transmission individually. Simultaneous voiceand data communications can be accomplished by equipping the receiverswith despreaders for discriminating voice and data information signalsspread by different PN codes.

In commonly-owned provisional application Ser. No. 60/248,182, whichapplication is incorporated by reference herein, there is disclosed anad-hoc, peer-to-peer radio system for use as a stand-alone system thatis also connected to a cellular network and/or PSTN. The ad-hoc mobileradio networking system thereof is capable of receiving and transmittingvoice, data and video calls through any number of different types oftelecommunication networks, such as the PSTN, the Internet, and thelike, besides the cellular and next-generation cellular networks.

Past research has shown that conventional Carrier Sense Multiple Access(CSMA) algorithms experience diminishing returns when networks approachtheir ultimate capacity. The vast majority of current research centerson channel access algorithms that provide transmission capacity over asingle shared medium. An example of this is the IEEE 802.11 wirelessstandard which employs a Carrier Sense Multiple Access/CollisionAvoidance (CSMA/CA) algorithm. All users within a Basic Service Set(BSS) share a common channel resource.

The ad-hoc, peer-to-peer radio system of the present invention is basedon a transport-mechanism using a time division duplex (TDD) technique ina code division multiple access (CDMA) system. Time Division Duplex(TDD) is a way of maximizing the bits/hz/km2. Such a system not only maybe used for providing commercial voice, but is also quite suited to bothtransmission and reception of data and video services. Time DivisionDuplex (TDD) systems are typically used for packet data systems, sincethey make much more efficient use of the available bandwidth, in orderto deliver a much higher effective data rate to the end user. TDD istypically used in fixed wired solutions or point-to-point wirelesssystems because it has its own spectrum limitations. TDD systems,however, have not hitherto been deployed for voice systems.

Unlike the personal communication radio system of U.S. Pat. No.5,943,322—Mayer, et al., the Time-Division Protocol (TDP) of the presentinvention does not care about the modem-type of access to radiospectrum, and is designed to work with or without a base station orgateway, since modem functionality is not part of the TDP of the presentinvention. The protocol of the present invention uses onecontrol/configuration channel and three or more data channels, wherecommunication between radio terminals is planned for preventinginterference. Time synchronization is independent of the communication,whereby no collisions among terminals are possible for configurationdata, excepting in the last time slot, and no collisions are possible inthe data channels, as described above. The protocol of the presentinvention may transmit data and video, in addition to voice, since eachis just another class of data

The system of the present invention is much more complex due tomultiple, parallel data channels that are coordinated by a singlereservation channel. In this system, a combination of CSMA/CA, TDMA(time division multiple access), FDMA (frequency division multipleaccess), and CDMA (code division multiple access) is used within thechannel access algorithm. The transceiver used in the system employs twomodems to solve the channel reliability issues with multiple channeldesigns, as disclosed in the above-described copending U.S. applicationSer. No. 09/705,588. Specifically, the system dedicates a receive-onlymodem for gathering channel usage information on the reservationchannel. The reservation channel operates a hybrid CSMA/CA and TDMAalgorithm. The remainder of the protocol uses FDMA for the multiple datachannels, and CDMA for multiple users on the same data channel.Reference is also had to copending, commonly-owned U.S. patentapplication Ser. No. 09/846,479, filed on May 2, 2001, entitled“Prioritized-Routing for an Ad-Hoc, Peer-to-Peer, Mobile Radio AccessSystem”, which is incorporated by reference herein, in which there isdisclosed an example of routing table messaging which may be used in thepresent invention.

SUMMARY OF THE INVENTION

It is the primary objective of the present invention to provide anad-hoc radio system as part of an overall, larger cellular network,and/or as a stand-alone, independent system, in order to providecommercial use for providing voice, data and video communicationsbetween radio terminals of the radio system of the invention and betweenequipment outside the system of the invention.

It is also a primary objective of the present invention to provide anoverall protocol for ad-hoc radio system not utilizing a fixed basestation, whereby a connection path by which a call is made takes intoconsideration the power loss associated therewith, in order to determinethe least-energy routing of a call for the particular service type beingtransmitted, such as voice, data or video.

The protocol of the present invention is based on a time-division duplex(TDD) plus code-division multiple access (CDMA) burst packet technologyused within the channel access algorithm of the system of the presentinvention. This provides the improvements in throughput and reliabilitythat are required to deliver high quality voice, video and data Thereservation channel implements a time division multiple access algorithmwith dynamic slot allocation. In a distributed manner, nodes determinegeographic reuse of slots based on channel quality. Signal qualitycalculations are used to determine the likelihood of a slot reusecausing destructive interference within a node's neighborhood. Requestsfor slot usage are compared with the known traffic pattern and acceptedor rejected by nodes within RF signal range based on the signal qualitycalculations. Additionally, the algorithm of the present inventionreadily provides for the mobility of nodes between geographic areasthrough the use of a special slot that is reserved for nodes withoutreservations. Nomadic nodes use this slot to locate a permanent slot toclaim for their use. Once claimed, the collision free properties can beenforced to improve the reliability and throughput of messages generatedby this node. This results in a maximal use of the spectrum within ageographic area.

The system of the present invention utilizes a method and algorithmwhich, in the preferred embodiment, is intended for an ad-hoc networksystem called “ArachNet”, and is based on least-energy routing of callsfrom and between network radio terminals. In simple terms, the majorcomponent of the routing decision is to choose the route to thedestination that uses the least amount of energy over the completeroute. The major reason for this is that least-energy routing minimizesthe radiated RF energy, in order to reduce interference betweenterminals. A consequence of this is that it creates the most efficientuse of the power supply of the terminals. Routing tables based on thisleast energy routing a developed by the system of the invention, andstored at one or more radio terminals, which routing tables aretransmitted and stored by other terminals forming part of the link bywhich a call is connected. An example of such a routing table isdisclosed in copending, commonly-owned U.S. patent application Ser. No.09/846,479, filed on May 2, 2001, entitled “Prioritized-Routing for anAd-Hoc, Peer-to-Peer, Mobile Radio Access System”, which is incorporatedby reference herein.

Variants or equivalents of the system of the invention are possible.There are a number of variants of this approach that would provideacceptable performance. These variants include tuning of each of thefour access schemes—CSMA/CA, TDMA, FDMA, and CDMA. For example, thewidth of the time slots may be adjusted based on the specific networkover which the protocol is executing. Performance of the network is verydependent on the number of parallel data channels which can be used. Abalance exists between the capacity of the reservation channel to makedata reservations and the capacity of the data channels to provideservice. This balance is dependent on the underlying capabilities of thededicated, reservations-channel modem that implements the protocol. Theperformance of the protocol is also dependent on the inclusion of thechannel quality extracted from the channel. Accurate estimates of thesignal strength translate into improvements in geographic reuse, whichcan be obtained by aggressive power control schemes. Another example isthe use of advancements in the codes used within the CDMA portion. Codeswhich improve the cross-correlation performance of terminals which sharea common data channel improve the throughput and reliability of theoverall network performance.

The adaptive power algorithm of system of the present invention leads toimprovements in the determination of RF radius for a given data rate.Increasing the data rate and reducing power promotes geographic reuse.Any loss in communication is easily compensated by our ad-hoc routingalgorithms.

The channel access approach of the invention is equally applicable forsubnets which include or do not include gateways. In the gatewayapproach, time is coordinated within the ad-hoc environment by thegateway. In the non-gateway approach, a distributed time algorithmprovides acceptable performance. In general, gateways permit thecreation of larger networks such as MAN's and WAN's.

While the protocol method of the present invention is disclosed withregard to an ad-hoc, peer-to-peer radio system, the protocol is equallyapplicable to any wireless LAN, wireline network, and the like, to whichthe method and system disclosed in copending U.S. application Ser. No.09/705,588 may apply.

BRIEF DESCRIPTION OF THE INVENTION

The present invention will be more readily understood with reference tothe accompanying drawings, wherein:

FIG. 1 is a logical flow chart showing the software structure of theprotocol of the system of the present invention;

FIG. 2 is depiction of the time-division of the TDD protocol (AP) of thepresent invention showing the time frames thereof with separated timeslots;

FIG. 3 is a depiction of the many terminals (AT) connected to aparticular gateway of the system of the present invention connecting theterminals to an exterior network, with one particular AT entering theservice domain thereof and the connection path thereof;

FIG. 4 is a depiction similar to FIG. 3, but showing the particular ATmoving away from the gateway and other AT's, whereby disconnection orreconnection must be carried out;

FIG. 5 is a depiction similar to FIGS. 3 and 4, showing a gatewayconnecting the system to outside networks, which connection path doesnot require very high speed, and where the total energy for passing dataalong the route is minimized;

FIG. 6 is a depiction of the time frames (TF's) with time slots (TS's)of the protocol of the system of the present invention required forperforming one hop between terminals (AT's) for a permanent link, inorder to assure proper communication;

FIG. 7 is a depiction similar to FIGS. 3–5, but showing the connectingroute between two AT's of a local link, in order to control powerrequirements of the AT's;

FIG. 8 is a graphical depiction showing an AT approaching a group ofAT's and the closed triangular connection therebetween;

FIG. 9 is a graphical depiction similar to FIG. 8 showing the opentriangular connection therebetween if the AT's experience powerreduction, whereby connection is preserved via the intermediate AT withensuing reduction in energy loss;

FIG. 10 is a graphical depiction similar to FIGS. 8 and 9 showing theperturbed power profile of the AT's and the connection therebetweenafter the lowering of the power of all of the AT's;

FIG. 11 is a graphical depiction similar to FIG. 10 and showing theclosed triangular connection therebetween after one time frame afterpower perturbation; and

FIG. 12 is a graphical depiction similar to FIG. 11 and showing the opentriangular connection therebetween after two time frame after powerperturbation with the ensuing steadystate, energy-saving path-connectionbetween the AT's.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of a better understanding of the description, the followingdefinitions and abbreviations are hereby given:

Definitions

“Service Area of a Terminal”

The geographical area where the transmission of a terminal can bereceived at a level higher than environment noise.

“Receive Set of a Terminal”

The set of terminals located within the service area.

“Transmit Set of a Terminal”

The set of terminals containing one particular terminal within theirservice areas.

“Service Set of a Terminal”

The set of terminals that can receive the transmission of one particularterminal and can be received at that terminal (the intersection betweenthe receive set and the transmit set).

“Simple Connection”

An abstract notion associated to two terminals that can communicate onewith another.

“Connecting Path”

A set of adjacent Simple Connections.

“Service Group of a Terminal”

The largest set of terminals containing at least one Connecting Pathbetween the host terminal and any other terminal of the set.

“Set of Active Time Slots”

All time slots used by the service set of a terminal.

“Source Terminal”

The terminal requesting the service.

“Destination Terminal”

The terminal requested to provide the service.

“Route”

The Connecting Path between the Source and the Destination of a service(voice, Internet access or data transfer).

“Link”

The Route, the Service and the transmitting plan at each hop along theroute.

“Isolated Network”

A network of terminals not connected to a gateway.

Abbreviations

AD Application data

Data required or generated by an application using AT for data transfer.Examples of such applications are: Internet browser, telephone, filetransfer server/client, Internet games, e-mail send/receive, shortmessage services, Internet radio/TV broadcaster/receiver, emergencyvideo/audio/text message broadcaster/receiver, report of appliance(including automotive) functionality status, teleconferencingvideo/audio participant, etc.

AP Arachnet Protocol

The protocol supporting the connection and data transfer between AT's.

AT Arachnet Terminal

The wireless terminal of the system of the present invention.

ATS Active Time Slot Set

The set of time slots that are used by an AT or its service set.

CD Configuration Data

Data exchanged in Configuration Channel for maintaining the connectivitybetween AT's.

CC Configuration Channel

The radio channel selected for exchanging Configuration Data (channelF0).

DC Data Channel

Radio channels used for exchanging Application data (channels F1, F2 andF3).

GW Gateway

The special type of fixed AT that provides connection to “the World”through “land” (not wireless) connections.

IFTG Inter Frame Time Gap

The time gap between the end of the last TS of a TF and the beginning ofthe next TF.

IN Isolated Network

The network not connected to the world. An IN has a root AT thatprovides the functionality needed for data routing and connectivity.

LLC Logical Link Control

The higher level of the protocol stack providing the interface betweenthe network and applications.

MAC Medium Access Control

The medium level of the protocol stack providing the control of theaccess to the radio spectrum.

PAL Physical Access Layer

The lower level of the protocol stack responsible for transmitting andreceiving data to/from other AT's.

RxS Receive Set

The set of terminals that can receive the signal transmitted by the ATowning the set.

SA Service Area

The area where the signal transmitted by an AT can be received at alevel higher than environment noise.

SG Service Group of an AT

The group of AT's that can be connected to the host AT with at least oneconnecting path.

SS Service Set

The set of AT's that can receive the transmission from the host AT andcan be received at the host AT.

TF Time Frame

A division of the time. The size of TF if configurable and depends onseveral environmental factors.

TS Time Slot

A division of the TF. The size and number of TS within a TF isconfigurable.

TxS Transmit Set of an AT

The set of AT's that can be received by the host AT.

The protocol (AP) of the system of the present invention applies to anad-hoc, peer-to-peer radio network system having coordinating channelaccess to shared parallel data channels via a separate reservationchannel, as disclosed in copending U.S. application Ser. No. 09/705,588.In the radio network system of the invention, there is no fixed basestation; each radio terminal is capable of acting as a mobile basestation. The protocol of the present invention provides such an ad-hoc,peer-to-peer radio system with the capability of preventing collisionsof data transfer. In high-density populated area (conference halls,stadium, downtown of big cities, etc.), the protocol of the presentinvention allows each terminal to perform close to its maximumtheoretical capacity, while dropping the requests in excess. Suchbehavior is in contrast with conventional polling-type protocols thatcannot provide any service when the number of requested connections islarger than a particular fraction of terminal capacity.

For implementing the protocol of the present invention, each terminal(AT) has fill information about all activities of other terminals andwill provide all other terminals with full information about its ownactivity. According to the present invention, a combination of TDMA(time division multiple access), FDMA (frequency division multipleaccess), and CDMA (code division multiple access) is used within thechannel access algorithm of the system of the present invention. Thisprovides the improvements in throughput and reliability that arerequired to deliver high quality voice, video or data. The reservationchannel implements a time division multiple access (TDMA) algorithm withdynamic slot allocation. In a distributed manner, nodes determinegeographic reuse of slots based on channel quality extracted frommessaging in a separate reservation channel. Signal quality calculationsare used to determine the likelihood of a slot reuse causing destructiveinterference within a node's neighborhood. Requests for slot usage arecompared with the known traffic patterns, and accepted or rejected bynodes within RF signal range based on the signal quality calculations.Additionally, the algorithm of the present invention readily providesfor the mobility of nodes between geographic areas through the use of aspecial slot that is reserved for nodes without reservations. Nomadicnodes use this slot to locate a permanent slot to claim for their use.Once claimed, the collision free properties can be enforced to improvethe reliability and throughput of messages generated by this node. Thisresults in a maximal use of the spectrum within a geographic area.

The system of the present invention utilizes a method and algorithm forad-hoc network system that is based on least-energy routing of callsfrom and between network radio terminals. In simple terms, the majorcomponent of the routing decision is to choose the route to thedestination that uses the least amount of energy over the completeroute. The major reason for this is that least-energy routing minimizesthe radiated RF energy, in order to reduce interference betweenterminals. A consequence of this is that it creates the most efficientuse of the power supply of the terminals.

In a medium dynamically changing its structure, superlative notions as“full connectivity”, “optimal configuration” or “best structure” are, infact, not applicable, because they cannot be exactly defined. Theprotocol of the invention makes full use of all available information(that may be incomplete or approximate) about other terminal activitiesand broadcasts full information about its own current or intendedactivity. Such cooperative attitude creates the capability to plan andcheck data-transfer planning before data transfer is initiated.

In most of the cases, the application data are exchanged betweenterminals using the same or less transmitting power than the power usedfor exchanging configuration data on the control or configurationchannel. This fact allows better use and reuse of frequencies and timeallocation, and makes the application data exchange less sensitive tointerference from hidden terminals (AT's).

For supporting the protocol of the present invention each AT of theradio system has the following capabilities:

-   -   Measures the level of received signal with very good precision;    -   Measures the level of received radio noise with very good        precision;    -   Controls the transmit power;    -   Changes fast from receiving to transmitting;    -   Changes fast the transmitting or receiving frequency;    -   Uses a dedicated receiver for listening to Configuration Channel        messages;    -   Controls the data rate; and    -   Uses a mean for network clock synchronization.

Software Architecture

Referring now to FIG. 1, the protocol of the invention is implemented asa three-layer software stack. The lowest, the Physical Access Layer(PAL) 10, is responsible for transmitting and receiving configurationand application data. It exchanges configuration data with the MiddleAccess layer (MAC) 12 and application data with the highest layer, theLogical Link Control (LLC) 14. Data is received and transmittedaccording with the communication plans elaborated at MAC. The MediumAccess Control (MAC) is responsible for processing receivedconfiguration data, for controlling the transmit power, data rate, forcreating the data transmit plans and for building the configuration datato be transmitted to the Service Set (SS) of AT terminals. It exchangesrouting data with the LLC and configuration data (power, data rate,transmit plans) with the Physical Access Layer. The protocol of thepresent invention is carried out in this MAC layer. As will explainedhereinbelow, when there exists an isolated network (IN) of terminals,the protocol of the invention is capable of being carried out by eachrespective AT. Control (LLC) layer is responsible for exchangingapplication data between applications and the Physical Access Layer(PAL). Data received from PAL is unpacked, decrypted and distributed toapplications. Data from application is encrypted, packed (adding routinginformation), and passed to the PAL to be transmitted.

The exchange of configuration data (CD) between AT's participating in anetwork of the present invention is accomplished in configurationchannel using frequency F0. The other channels (F1, F2, F3) are used fortransferring application data (AD) between AT's, thus constituting FDMAscheme of the multiple aspect protocol of the invention.

The Protocol of the present invention uses a time division scheme (TDD)for organizing the access to airwaves. Referring to FIG. 2, the time isdivided in time frames (TF) 16, and each frame is divided in time slots(TS) 18. At the end of each time frame is the Inter Frame Time Gap(IFTG) 20 that has a different length than the regular TS. During theIFTG, no data is sent out by any AT, so that each AT processes datacollected from other AT's during the time frame, and will performrequired calculations, such as power level, data channel connectivity,etc.

A terminal (AT) can transmit configuration data in F0 only during itsown assigned Time Slot (TS). Initially, an AT signals its presence usingthe last TS of the time frame. With the next time frame, it mustrelocate to another TS with a lower rank, that is one earlier in thetime frame. This relocation policy reduces substantially the possibilityof collisions in the configuration channel. If two or more AT's try tostart working during the same time frame (TF), their transmissions maycollide, but the collision is identified and corrected by means ofconventional PN coding (CDMA). The probability of collision in the datachannels (DC's) is almost zero for AT's, since the reservation channelinformation exchange has already ensured such a collision-freetransmission, either by way of the chosen data channel for transmission(FDMA).

The power level of the modem for the configuration channel (CC)information is greater than that of the modem for transmitting data onthe data channels (DC), since an AT must first send out connectivityinformation with enough power to reach other AT's of its respectiveservice set (SS). Once this has been done, and a routing pathdetermined, which routing path will indicate the first AT that shallconstitute the first hop or link of the routing path, which hop iscloser to the requesting AT than at least most of all of the other AT'sof the SS, the other modem dedicated to the transmission of data on theDC's will only have to transmit at a power level less than that of themodem dedicated to the configuration channel. Thus, since applicationsdata (AD) are transmitted at a lower power than that of theconfiguration data (CD), the condition for collision in data channelscan be identified before it occurs, with appropriate measures beingtaken for preventing it, such as the use of CDMA. In addition, since thedata channel data is transmitted at a lower power level, interference isreduced since the RF waves of the data channels do not propagate as faralong the SS. It is noted that in the case where the primary modem isused most of the time for transmitting both configuration data as wellas channel data, with the dedicated reservation-channel modem only beingused when the primary modem is occupied with sending out messaging onthe data channels, the primary modem will have its power level changedin accordance with which channel it is transmitting, as disclosed incopending U.S. application Ser. No. 09/705,588. However, in thepreferred form of the invention, the dedicated configuration-channelmodem receives and transmits configuration data regardless of the stateof the primary modem.

At very heavy loading, the degradation of the service provided by theprotocol of the present invention is expected to remain constant, incontrast with prior-art polling-type protocols that collapse abruptly insimilar conditions.

Operation

When first powered on, or when approaching a group, the new terminal(AT) listens to messages in the time frames (TF), creates a utilizationmap based thereon, and computes its transmit power, in the mannerdisclosed in copending U.S. application Ser. No. 09/705,588. Accordingto the protocol of the present invention, it submits the first messagein the last time slot (TS) of the time frame, using as much power asneeded in order to reach all AT's from which it has received similarmessaging, that is its service set (SS). The message shows theutilization map it knows about, and requests to register with theclosest AT. In the utilization map, it marks as busy all time slots (TS)during which a message or high-level noise was received during the lasttime frame, and also marks the time slot where it intends to move towith the next frame. The TS where it wants to move in the next timeframe will have been reported as free in utilization maps of all AT's ofthe SS. In every time frame, the AT creates the utilization map based ontime slots it identified as being busy (a signal was received during theTS), and it receives similar maps from all other AT's in thetransmit-set of each AT (TxS). Identifying free TS's consists in makinga bit-wise OR between all received maps. The result shows free timeslots as bits with value zero and busy TS as bits with value one.

The Configuration Channel (CC) is used for passing two kinds ofmessages: connectivity and data transfer plans. All messages in theconnectivity group contain the utilization map, the power used fortransmitting the message, and the level of environment noise at atransmission site, beside other, specific, conventional information.These messages register, un-register, and communicate the respective ATstatus. The status message is transmitted whenever no other message ispending in order to maintain connection.

The group of messages for data transfer planning is used for adjustingthe transmit power, building, re-building, re-routing and releasinglinks, as described hereinbelow in detail. As disclosed in copendingU.S. application Ser. No. 09/705,588, some of them are used beforestarting the transfer of data packet, and some are used while the datatransfer takes place. Data Channels (DC's) are mainly used for movingdata packets from one AT to another. Some of the data transfers requireconfirmation/rejection of received data, and some not. A rejection ofreceived data is an automatic request for retransmitting the associateddata package. Broadcast services do not require any confirmation ofreceived data correctness.

Connectivity Connected Network

In order to talk to the “world”, each AT should be connected directly orindirectly to a gateway that connects the AT's of the service group ofAT's (SG) to an outside network, such as a cellular network, PSTN, andthe like. When it is connected indirectly, the connectivity is realizedthrough another AT or AT's. An AT loses its connectivity if an uplink AT(an AT closer to the gateway along the connection path) becomes out ofrange (cannot be heard anymore), or if the uplink AT loses itsconnectivity. The AT so losing its connection will look for the closest(smallest path loss) connected AT providing the smallest path loss ofpower, and reconnect through it. If no connected AT is found in thecurrent service set (SS), the disconnected AT will send out statusmessages every time frame (TF). The transmit power of that AT isincreased one dBm every other TF, until another, connected AT answersback. If after reaching the maximum transmitting power (28 dBm) noconnected AT can be included in the SS, the AT and its SS are consideredas isolated. An SS can be isolated only if the SG containing the SS isisolated, also. An isolated AT will adjust its power according with thepower and space topology of its SS. Periodically, isolated AT's willtransmit messages using the maximum transmitting power until it is heardby a connected AT that provides the connectivity to the world via agateway. While an SG is isolated, the services can be provided onlybetween those terminals-members of the service group (SG). An AT thathas no service set (SS) will send out messages every 60 seconds usingthe maximum power. The self-testing functions will be activated beforesending out any high-power message to verify hardware viability, sinceimproperly working AT's can disable the network by sending outinterfering signals.

When the AT is powered on, it listens to the transmit set (TxS) fromother AT's. It identifies the path loss for each TxS member bysubtracting the strength level of the received signal from the transmitpower. The highest path loss is used for setting the current transmitpower in the configuration channel (CC). The new AT submits aregistration request to the closest (smallest path loss) connected AT inthe last TS, as described above. The registration request is forwardedto a gateway for use by the LLC layer software. Each terminal along thepath remembers the fact that it helped to register the new AT. The firstuplink AT is responsible for monitoring the activity of the newlyregistered AT, and submits a request to unregister it in case it becomesout of range, or if it was heard requesting registration with anotherAT.

Referring to FIG. 3, AT7 is shown entering the network. The connectingprocess and the information held at each AT in this network is asfollows:

AT7

1. Submits the registration request to AT6;

2. Monitors the evolution of path loss to all received AT's and adjuststhe transmit power according with path loss variation and noise level ineach AT area; if AT6 is predicted to get out of range in next 5 seconds,AT7 searches for another AT to connect through;

3. Monitors the registration status of the AT6.

Connectivity data: Uplink—AT7 Downlink—none:

AT6

1. Submits the received registration request of AT7 to AT3;

2. Monitors the path loss to all received AT's and adjusts its owntransmit power according with path loss variation and the noise level ineach AT area; if AT7 becomes out of range, it submits to AT3 the requestto unregister AT7;

3. Monitors the activity of AT7; if it identifies that AT7 requestsregistration with another AT, AT6 submits to AT3 the request tounregister AT7;

4. Monitors the evolution of path loss to AT3; if AT3 is predicted toget out of range in next 5 seconds, it searches for another AT toconnect through;

5. Monitors the registration status of the AT3.

Connectivity data: Uplink—AT3 Downlink—AT7:

AT3

1. Submits the received registration request of AT7 to Gateway;

2. Monitors the path loss to all received AT's and adjusts its owntransmit power accordingly; if any of AT4, AT5 or AT6 becomes out ofrange, submits to Gateway the request unregistration the AT;

3. Monitors the activity of AT4, AT5 and AT6; if any of them requestsregistration with another AT, submits the un-register request to theGateway;

4. Monitors the evolution of path loss to Gateway; if it is predicted toget out of range in less than 5 seconds, it searches for another AT (orgateway) to connect through.

Connectivity data: Uplink—Gateway Downlink—AT4, AT5, and AT6/AT7:

Gateway

1. Submits registration of AT7 to the global database;

2. Monitors the evolution of path loss to all AT's it can receive andadjusts its own transmit power accordingly.

Connectivity data: Uplink—world Downlink—AT1/ . . . , AT2/ . . . , andAT3/AT4, AT5, AT6, AT7.

The registration process creates a tree structure rooted at the gateway.Each AT knows the uplink through which it registered, and the list ofdirect downlinked AT's from the AT requesting registration. To eachdirect downlink is associated the list of AT's registered through it. Ifany AT is turned off or loses the connection with its uplink, the uplinksubmits the request to unregister the AT that has lost the connectionand all its downlink AT's. The unregistration requires all AT'sreceiving and transmitting to remove the information about theunregistered AT's from their lists.

The Gateway sends to the Global Database only registration requests. Asa result, the Global Database remembers the Gateway where the AT wasconnected last time.

Referring now to FIG. 4, it is shown the case where AT6 is moving awayfrom AT3, with which it had been registered and by which it had beenconnected to the gateway 22. As result, it requests to register with AT5by sending a message thereto. AT3 listens to this request, and submitsto Gateway 22 the request to unregister AT6 and AT7. If AT3 cannot hearAT6 requesting to re-register, it means that the AT6 is out of the rangeof AT3 and that AT3 must submit to Gateway 22 the request to unregisterAT6 when the condition occurs. If the request from AT5 to register AT6comes before the time-out, AT3 has only to update the connectivity databy moving the AT6 downlink list to AT5 downlink list.

If AT3 can hear AT6, the process develops as follows:

Transmit Transmitter Frame Transmit data Update Receiver Receiver Update1 AT6 Self Replace uplink AT5 Open AT6 downlink register AT3 with AT5list with AT5 1 AT3 Move AT6 downlink list (AT6 and AT7) to un-registerlist 2 AT3 Un-register Remove AT6 from Gateway Remove AT6 from AT6un-register list AT3 downlink list 2 AT5 Register AT3 Add AT6 to AT5 AT6downlink list 2 AT6 Register AT5 Add AT7 to AT6 AT7 downlink list 3 AT3Un-register Remove AT7 from Gateway Remove AT7 from AT7 list AT3downlink list. 3 AT5 Register AT3 Add AT7 to AT5 AT7 downlink list 4 AT3Register Gateway Add AT6 to AT3 AT6 downlink list 5 AT3 Register GatewayAdd AT7 to AT3 AT7 downlink listIf AT3 cannot hear AT6, the process develops as follows:

Transmit Transmit Transmitter AT Receiver Frame AT data Update ATReceiver Update 1 AT6 Self Replace uplink AT5 Open AT6 downlink registerAT3 with AT5 list with AT5 2 AT5 Register AT3 Add AT6 to AT5 AT6downlink list. Since AT6 was a direct downlink, all its downlink list ismoved to un-register list. 2 AT6 Register AT5 Add AT7 to AT6 AT7downlink list 3 AT3 Un- Remove AT7 from Gateway Remove AT7 from registerun-register list AT3 downlink list. AT7 3 AT5 Register Add AT7 to AT6AT3 Add AT7 to AT5 AT7 downlink list downlink list 4 AT3 RegisterGateway Add AT6 to AT3 AT6 downlink list 5 AT3 Register Gateway Add AT7to AT3 AT7 downlink list

The “unregister list” contains all AT's to be unregistered. Noregistration request is processed if the “unregister list” is not empty.

All operations described herein are executed in the configurationchannel (CC) only. If any of the AT's involved in connectivity updateare supporting data transfer at the time, the data transfer is notaffected.

Isolated Network

When powered on, each terminal is isolated. The AT tries to find aregistered AT and register to the world through it through a last timeslot of a time frame, as described above. The search consists in sendingout status messages and listening for answers. At first, the AT listensin the configuration channel (CC). If no other AT can be heard, ittransmits the status message in a time slot (TS) randomly selected. Withevery time frame (TF), it increases the transmitting power until aresponse is received. The response may be from a gateway 22 or otherAT's. In the next step, the requesting AT requests the registration withone of the correspondents in the following priorities: The closestgateway, the closest AT registered with the world, or the closest ATregistered with an isolated network. If no response is heard and thetransmitting power is at maximum level (28 dBm), the AT is, therefore,isolated, and becomes the “roof” of an isolated network (IN). Theidentification of the IN is the time in seconds since the Jan. 1, 2001when the AT was powered on, or another similar method.

All members of an isolated network (IN) send out the status message atmaximum power level (28 dBm) at a random rate, varying between 10 and Nseconds, where N is three times the number of members in the IN. Themessage is sent in the last time slot (TS) of the first time frame (TF).AT's in the same IN do not adjust their power based on the messagereceived during the last TS of the first TF. The message is intended toidentify the possible connectivity to another IN or to connectednetworks. The AT, including the root, that can hear AT's from more thanone isolated network (IN), should request registration with the closestAT member of the IN with the largest identification number (the older).This method will create in an IN a tree structure similar with thestructure of a connected network (CN).

Routing

Most of the time, AT's are connected to the world through a gateway orgateways 22. In some particular cases, a group of AT's can be isolatedfrom the world, if no functioning gateway is available. Routing datathrough an isolated network (IN) is no different than routing datathrough a connected network (CN).

Powering a Link

For supporting the transfer of data between AT's, the protocol (AP) ofthe present invention uses the concept of a “link”. The link is theselected route connecting the source AT to the destination AT orgateway, and includes: The type of service provided, such as voice, dataor video; the time slot (TS) used on each AT hop for transporting data;and, indirectly, the application instantiation. Between an AT and agateway there may be active in the same time many links each supportinganother application or instance of the same application. Applicationdata is usually transferred between the AT and associated gateway by thelink, using a sequence of many AT's. The AT-connectivity process createsa connectivity path between the terminal and its gateway. Theconnectivity path uses the smallest possible power, which, therefore,implies the use of a large number of hops and a large pipeline delay,which is permissible when the class of service is data transfer.

Referring now to FIG. 5, there is shown the connection path of:Gateway→AT3 →AT5 →AT6→AT7. This may be used to support the link thatpasses data for applications not requiring very high speed, or acceptinglarge delay or latency. Thus, the total energy used for passing dataalong this route is the smallest possible. Over the connectivity createdby the longest path, one has the route Gateway→AT3→AT7 that has only twohops, and may be used for exchanging data with applications requiringsmaller delays such as voice or video transmission. The connectivityroute Gateway→AT7 has one hop only, but it requires much more energythan any other route. A high-energy route implies the use of hightransmit power for transmitting the data. According to the presentinvention, in order to prevent unexpected interference, the transmittingpower in the data channels (DC's) are the same or lower than thetransmitting power in configuration channel (CC). In order to ensure thefull cooperation between AT's, the whole service group (SG) will adjustits power in the configuration channel (CC), even if only one route hasa real need for it, as described hereinbelow.

The use of high transmit-power has two side effects. It drains thebattery of mobile AT's faster, and reduces the availability of systemresources, making it difficult to reuse frequency and time slots. If theconnection path between the gateway 22 and the client AT has N₁ hops,and the gateway power is P₁, and the length of the connection routeshould be no more than N₂ hops, the new power to be used at each end ofthe path is P₂

$\begin{matrix}{P_{2} = {P_{1} + {\left\lceil {30\lambda\;{\log_{10}\left( \frac{N_{1}}{N_{2}} \right)}} \right\rceil\mspace{14mu}{dBm}}}} & \text{(0-1)}\end{matrix}$Equation (0-1) provides a means to compute the new, greater power P₂that should make the path to have only N₂ hops. The parameter λ is the“space absorption” factor. Its value is dependent on many factors,including the propagation media characteristics, such as free space,concrete walls and floors, wooden walls, metal frame structure, foliage,and the like, lateral reflections, vertical reflections, etc. Theinitial value for λ may be 1.0, but it should be adjusted based onsystem reaction to the intent to the changing of the number of hops.

The corrected power is applied at the gateway and at the client AT, afact that attracts automatic change of the power profile along theentire connection route. If the correction does not have the expectedresult, a second correction will be applied after the route has beenestablished.

Messaging Based on Least Energy Routing

The protocol of the present invention is based on least energy routingdetermination, as discussed previously especially when transmittingdata. The routing table messaging that is exchanged between termimalsmay have format as that disclosed in copending, commonly-owned U.S.patent application Ser. No. 09/846,479, filed on May 2, 2001, entitled“Prioritized-Routing for an Ad-Hoc, Peer-to-Peer, Mobile Radio AccessSystem” which is incorporated by reference herein.

of the protocol of the invention is used to set up the optimal path of acall. The following algorithm of the protocol of the present inventionis based on this minimum energy routing.

-   -   source-routing (message_ptr,msg-length,destination, msg-type)    -   /* source based routing including link adaption algorithm    -   */    -   opt_route(destination, msg_type)    -   /* determine optimal route to destination this will return the        best available route based on Class Of Service (COS) from        msg_type and other network parameters including link quality.        The returned information will be used to calculate the data rate        and power level    -   */    -   calc_symbol_rate (sym_rate)    -   calc_code_rate (code_rate)    -   calc_pwr_level (pwr_level)    -   send_msg(RTS,msg_length,destination,sym_rate,code_rate,pwr_level)    -   /* send RTS to first router and await CTS to send the data        packet

-   opt_route (destination, msg_type)    -   RTS refers to Request-To-Send message; CTS refers to        Clear-To-Send message; msg refers to the message sent from each        terminal.    -   /*The following algorithm determines the best route to the        destination based on the COS in the message type.

The following example illustrates the decision process:

-   -   Route1 term1→term4    -   Low latency, BER=high    -   Route 2 term1→term2→term4    -   High latency, BER=low    -   Route 3 term1→term2→term3→term4    -   High latency, BER=low    -   Route 4 term1→term5→term6→term4    -   Low latency, BER=low    -   BER is Bit-Error-Rate; latency is delay.

In the case of a voice call that has a COS that can tolerate a high BERbut not high latency, it would choose route 1 over route 4 because itcannot tolerate high latency.

In the case of a data call that has a COS that can tolerate high latencybut not high BER, it will choose route 2 or route 3.

Linking

The protocol (AP) of the present invention defines permanent andtemporary links. A permanent link remains active until it is changed orreleased, while a temporary link is used only once. Permanent links areused for transmitting any type of information, such as voice, data andvideo. The subsystem providing the information may not be able toprovide it at a constant rate while the link is being planned. If thereis no information to be transmitted when the transmission time comes,the AT sends a “maintenance” package which has no other reason otherthan to maintain the link active, and to give the next hop theopportunity to measure and reply regarding transmission quality. Themaintenance packages are also created at a gateway 22 when theland-network is late and provides no data, or at any AT that receivesincorrect data and has no data in link queue. The maintenance packet isdropped if the receiving AT has data packets in link queue. Otherwise,the maintenance packet is sent to next AT in the link. A hop of the linkis released (removed from AT data structures) when no data, nomaintenance packet and no noise is received in the first time slot (TS)of the link hop. The lack of transmitted data is always followed by anabundance of data exceeding the capacity of the planned link. Packets ofdata have to be stored and planned for transmission in proper sequenceorder. A configuration parameter, combined with measurements of deliveryrate, is used for identifying when the amount of accumulated datarequires special action. Such action could be to drop some data inexcess, or to send out some of it using temporary links.

The permanent link is initiated when a service calls the client AT orthe client AT calls a service. The source AT and the gateway identifythe depth, the number of hops between the gateway and the AT, of theclient AT. The required number of hops is computed according withservice requirements. The gateway and client AT transmitting power inthe configuration channel (CC) is computed using equation (0-1). Foreach hop, the power in the data channels (DC) is computed based on powerloss to the next hop. If needed, the power used in the configurationchannel (CC) is increased, such that it is at least 2 dBm higher thanthe data-channel transmits power. The transmit plan is built using onlyfree TS's and TF's. The link message transmitted to the next hopcontains the transmitting plan. If any member of the service set (SS)identifies any conflict in the transmitting plan, it answers backshowing the channel and the map of the time frame (TF) conflicting withthe plan. In such case, a new plan is issued using the newly achievedinformation. When the plan has no conflicts, the next hop accepts it byissuing a confirmation.

Referring to FIG. 6, it takes at least two time frames per hop formaking the connection. In the first time frame (TF), the transmitting ATsends out the transmit plan as a Request-To-Send (RTS) message. In thenext TF, it may receive rejections from other AT's, including the nextAT in the route as Not-Clear-To-Send (NCTS) messages. If there arerejections, the transmitting AT issues a new transmit plan and sends itout in a third TF. The receiving AT can send the Clear-To-Send (CTS)message in the third TF, but it also has to listen if no transmit planwas reissued during the same frame. For assuring proper communication,the transmit-plan issued at AT11 must not use for transmitting data thetime slots (TS) that AT11 and AT12 are using for communication in theconfiguration channel (CC). When the permanent link is not neededanymore, a message that requests releasing the link is issued.

A temporary link is initiated when the amount of informational datapertaining to a permanent link passes over a predefined limit, and it istoo large to cover the network jitter. The initiator AT sends a requestfor a temporary link which includes the transmit plan. If any member ofthe service set (SS) finds any conflict in the plan with the currentlyassigned time frame (TF) and time slot (TS), the information onconflicting data channel is transmitted. The issuer AT has to makeanother plan and re-transmit it. The next hop confirms the plan. Ittakes at least three TF's to fully define a temporary link. It meansthat the temporary link must target time slots that are in time framesat least three TF's ahead.

Local Link

The local link is defined as a link between two AT's connected to theworld through the same gateway or two members of the same isolatednetwork (IN). FIG. 7 shows the connecting route between AT4 and AT7. AT4requested the link to AT7. Depending upon the type of required service,it increases its power, and sends the request for power adjustment toAT7. The request is used for identifying a connection route between thesource and destination, and to control the power at both ends based onservice requirements. Since AT4 does not know where AT7 is located, itissues the power control message toward the gateway or the root AT. AT3receives this request and finds AT7 in the AT5 downlink list. It thendirects the message toward AT5. AT5 directs the request to AT6, and thenAT6 directs it to AT7.

In local links, the request is always started at an AT, which sends ittoward the gateway or root AT. While the requests advance, thedestination AT is checked in local lists of each node. If it is found,the link-request is routed toward the destination. If the link-requestarrives at the gateway and the destination AT is not in gateway list ofregistered AT's, the request is passed to the world that may reject itor connect to the service provider. In contrast with the gateway, theroot of isolated network (IN) rejects the link if the destination AT isnot in its registration list.

Building the Link

The process of building a link has two steps. In the first step, therequest for setting the link power travels from the source to thedestination. The trace of the message is saved in each AT along theconnection route. The message carries information about the length ofthe path, which is incremented while the message is passed from one ATto the next. The power control request does not require confirmation.The sender listens in the next time frame (TF) if the next hopretransmits the message. If it does not, the message is repeated. Thesource increases its transmit power when sending out the power controlrequest based on its distance to the gateway, or the root AT if in anIN. When the message arrives at the end of the connection path, thedestination increases its transmit power in accordance with length ofthe path and service requirements. Then the destination sends out adummy Clear-to-Send (CTS) message using the new power. As response tothis message, all AT's that can hear it, and were part of the connectionpath for the link, answer with their Ready-To-Link (RTL) message. If thedestination made a substantial change in transmitting power, it has towait several frames until the service set (SS) stabilizes. After that,the source AT can select the proper AT from all of the answers from AT'sin order to build the first hop, based on that AT's position along theconnectivity route. While the link-hop is created using RTS/CTS/NCTSmessaging, all AT's along the connectivity path that can receive theRTS/CTS/NCTS messages answer with a RTL message. When the second hop isready to be built, the second AT in the link has data for selecting thenext AT in the path.

In FIG. 7, it is shown that AT6 answered the dummy CTS submitted by AT7while it was increasing its power. Then AT7 issued the RTS to AT6. WhileAT6 was confirming the link-hop by sending a CTS message, AT4 and AT5received it, and answered with a RTL message. AT6 selected AT4 for thenext hop because it has the smallest distance from the source as opposedto AT5.

Building the link takes a relatively long time in the protocol (AP) ofthe present invention, but after it is built, the link remains activefor a long time. Disconnections due to network mobility are repairedwhile information is transferred, and do not require the redoing of thewhole procedure. The power of each AT participating in the respectivelink is adjusted dynamically in order to maintain the properservice-quality and network connectivity.

Rerouting

For AT's not supporting a link, the transmitting power in theconfiguration channel (CC) is computed based on the AT's relativepositions within the service group (SG). As an AT moves, it mayre-register with the same or with another gateway. An active link ismore rigid and follows the changes in the connectivity tree at a slowerpace. The AT's supporting the link have their power in the configurationchannel (CC) and data channels (DC) controlled by the group topology andthe type of supported service. When an AT predicts that itsuplink-connection will go out of range, or it is already out of range,it changes its uplink-connection and registers with another AT. The newregistration may or may not change the gateway to which the AT waspreviously registered. After the registration request, the AT sends outthe request for setting the transmit power and the request for reroutingthe link(s). Then, it registers all sources and destination of supportedlinks. Finally, the AT sends out the request to register all other AT'sthat have registered through it. Information from the gateway startsflowing through the new route as soon as it is connected. Informationtowards the gateway is directed to the new route after a delay of timeframes depending on the type of service provided. For slow connections,such as data, the delay is twice the requester distance to the gateway.For fast connections, such as voice and video, the delay is equal withthe requester distance to the gateway.

Re-link

Each data transmission is confirmed with an acknowledge (ACK) message.NACK message is used for marking improperly received data that have tobe retransmitted. The failure of data reception can be caused bymulti-path, co-channel or adjacent channel interference. Usually,lowering the transmission rate solves the multi-path interference.Re-planning the link segment solves the co-channel and adjacent channelinterference. A RELINK message is used for establishing a new transmitplan between two adjacent AT's of the same link.

Length Adjustment

The destination AT of the link can measure the delay and can decide toreduce it. The adjustment process starts with increasing the power inthe configuration channel (CC) and sending the power-request message tothe source. A dummy clear-to-send (CTS) message is issued for selectingthe AT for the first hop of the link. The re-link request is sent tothis AT that continues the process, until it reaches the source. There-link request travels against the informational flow. Information isdirected onto the new segments of the route at the AT's shared by thenew and old routes. The old segments of the route are released, since nodata is sent through them anymore.

Regarding data packets, since they have sequence numbers, afterrerouting a link, the destination AT could receive the data packets inincorrect sequence. It must send them in proper sequence. Therefore,late, out-of-sequence packets get the highest transmission priority.

Power Control

The control of power is important for maintaining the connectivitybetween service group (SG) members and the quality of informationaltransfer.

Oscillation

The service group (SG) of AT's using the protocol (AP) of the presentinvention has the tendency to stabilize at a power profile that reflectsthe relative path loss between terminals. This “stabilization” is not100% accurate, because decisions made at one time frame (TF) are basedon measurements made during the previous TF. At the time the decision isapplied, the group has already changed its status. For this reason, thegroup power-profile may have oscillations around its stable position.For preventing this oscillation, the transmit power in the configurationchannel (CC) is filtered using the power used in last three time frames(TF's). If there is a repeat of the transmit power-level in last threeTF's, the current transmit power-level is computed with the averagebetween the currently computed power-level and the transmit power-levelused in previous TF; otherwise the last computed power-level is used astransmit power-level.

Variation

In the configuration channel (CC), each AT listens to all terminals andmeasures the level of the received signals. The difference between thetransmit power-level that is part of the received message and thepower-level of the received signal provides the measure of the loss ofsignal due to propagation. After listening to its service set (SS), a ATselects the largest path loss and adjusts its power-level to be able toreach that terminal at a power-level higher than the local noise. Theprotocol of the present invention makes the supposition that the pathloss between any two terminals is symmetrical, excepting for localnoise. In reality, the computed “signal loss” is not symmetrical in bothdirections, as receiver sensitivity and transmitter efficiency havevariations from one terminal to another due to parts variety,manufacturing process, tuning, or terminal aging. The protocol (AP) ofthe present invention can properly control channel access if thesevariations are less than ±5 dB.

Each AT keeps historical data about path-loss evolution for predictingthe connection-status in next 3–5 seconds. Equation (0-2) provides asimple method for acquiring the path loss variation, as described below.From measurements P(t₁) and P(t₂) of the path loss at time t₁ and t₂,the average path loss variation δ(t) is computed using an IIF:

$\begin{matrix}{{\delta\left( t_{2} \right)} = {{\left( {1 - k} \right)\;\delta\;\left( t_{1} \right)} + {k\mspace{11mu}\frac{{P\left( t_{2} \right)} - {P\left( t_{1} \right)}}{t_{2} - t_{1}}}}} & \text{(0-2)}\end{matrix}$The factor k has a very small value (0.01 for example) that areidentified empirically. If the measurements are performed every timeframe (TF), the difference t₁–t₂ is always one. Then the equationbecomes:δ=(1−k)δ′+k(P−P′)  (0-3)In this equation, P and P′ are the values of path loss measured in thecurrent and the previous time frames (TF's), and δ and δ′ are the valuesof the average variation of the path loss for the current and previousTF.

The average value of the path loss is computed with equation (0-4):L=(1−k)L′+kP  (0-4)In this equation, L is the average path loss, L′ is the previous averagepath loss, P is the last measured path loss, and k is the same filteringconstant as before. The predicted value of the path loss after m timeframes is computed with equation (0-5):PL=L+mδ  (0-5).If the predicted value of the transmit power that is computed based onthe predicted path loss and the noise at correspondent AT is larger than28 dBm, the connection will be lost in m time frames. Since the increaseof power in one AT can cause the whole group to increase the transmitpower, the AT may decide to re-register using another AT if it ispossible, where such decision may reduce substantially the transmitpower. After re-registering, the AT that supports at least a link shouldrequest to reroute it.

Optimization

When an AT moves away from its service group (SG), the transmit power isincreased in order to maintain the connectivity. When an AT moves closerto its SG, the connectivity is preserved, if using the currentpower-level, but this may not be economical. In FIG. 8, there is shownAT13 approaching its service group (SG). The transmitting power of allmembers of this group is high enough to allow each AT to communicatewith the other two. If AT11 and AT13 reduce their power, they can stillbe connected through AT12. The condition supporting the decision tolower the power of AT13 and AT11 is that AT12 must be able to talk withboth of them.

In FIG. 9, there is shown the transmit area of each AT after loweringthe transmitting power. AT12 is located in the intersection of transmitareas of AT11 and AT13, while AT11 and AT13 are in the transmit area ofAT12. It means that at this power profile, AT12 can communicate withAT11 and AT13, but AT11 and AT13 cannot communicate with each other. Thesystem's total transmit power is smaller than it was before. Theprocedure can be repeated until no triangle is formed. This procedurerequires that AT11 and AT13 know that both of them can talk to AT12. Theinformation must be achieved by listening to network “talk” which can beincomplete at any time.

The same effect can be achieved through a much more simple procedure.The system of AT's has the tendency to stabilize at a particular powerprofile. After applying a perturbation, the system returns to the sameor to another stable state. If the perturbation consists in lowering thepower, the new stable position will be, conditions permitting, at alower power. As with the triangle method, the perturbation should beapplied to all AT's in the system at the same time.

In FIG. 10, there is shown the situation after lowering the power of allAT's by one dBm. While using the perturbed power profile, AT11 can hearonly AT12, AT12 can hear AT11 and AT13, while AT13 cannot hear anybody.Based on this situation, AT11 identifies that it can remain connected toAT12 while using a lower transmit power. AT12 identifies that itstransmit power is too low for maintaining the connection to AT13. AT13considers itself isolated because it cannot hear anybody, and,therefore, increases its transmit power by 1 dBm.

In FIG. 11, in the next time frame, AT12 and AT13 return to the powerlevel they had before the perturbation, while AT11 uses only as muchpower as needed for remaining connected to AT12. In the next time frame,AT11 can hear AT12 and AT13, but it uses too little power to transmit toAT13. It decides to increase to the level it was using before theperturbation. The oscillation filter identifies it as a possibleoscillation and does not allow an increase larger than half of theincrement. AT12 can hear both AT11 and AT13 and finds that its currenttransmit power is correct for talking with both AT's. AT13 can hear onlyAT12. It finds out that the power it uses for such connection is toolarge, and computes the new, lower transmit power using data collectedfrom AT12.

In FIG. 12, there is shown the situation two time frames after applyingthe perturbation. AT12 and AT13 are both using the right power level forproviding the connection. AT11's transmit power is too high to talk toAT12, the only AT it can hear. With next time frame, AT11 will reducethe power to the proper level. After that reduction, all AT's will havethe same transmit power as the power computed using the triangle method.

Both methods require that the algorithm be executed in the same timeframe on all AT's. The triangle method can be applied every time frameor only at predefined times. The perturbation method can be applied onlyfrom time to time, but no sooner than 5 time frames, to allow the groupto get in a stable position.

The triangle method provides the final power profile after one timeframe, but it requires special computation for identifying whichtriangle can be broken. The information needed for this method iscollected while listening to other AT's talk, a fact that may not bepossible when supporting an active link.

The perturbation method requires three time frames to get to the rightpower profile. It does not require special computation, as the powercontrol algorithm is run every time frame anyway.

While a specific embodiment of the invention has been shown anddescribed, it is to be understood that numerous changes andmodifications may be made therein without departing from the scope andspirit of the invention as set forth in the appended claims.

1. A protocol for use in an ad-hoc, peer-to-peer radio system comprisinga series of terminals where each said terminal is capable of making atleast one of an outgoing call or receiving an incoming call, and whereeach said terminal comprising computer means, memory means for storingprogram software means therein, and where each said terminal is capableof being hop of a routing path connecting a call from a source to adestination, comprising: software means for said memory means of eachsaid terminal, said software means comprising means for generatingcommunications-information for transmission based on time-divisionmessaging; said communications-information comprising a series of timeframes (TM) each divided into a series of time slots (TS); saidcommunications-information comprising at least one time slot in whichcontrol-channel (CC) messaging information is transmitted, and othertime slots in which is transmitted channel data (CD) messaginginformation; each said time frame (TF) comprising a last time slot; saidsoftware means further comprising means for generating initial controlcommunications-information in a respective said last time slot (LTS) ofa respective said time frame (TF) indicating initial presence of arespective said terminal in order to start communicating with other saidterminals.
 2. The protocol for use in an ad-hoc, peer-to-peer radiosystem according to claim 1, wherein the length of each said time slotfor transmitting said communications-information is equal to each other.3. The protocol for use in an ad-hoc, peer-to-peer radio systemaccording to claim 2, wherein said software means further comprisesmeans for switching transmission of initial controlcommunications-information from said last time slot (TS) to another,free, earlier time slot of a subsequent time frame (TF) in order toreduce the chance of collision with other said terminals also initiallyregistering.
 4. The protocol for use in an ad-hoc, peer-to-peer radiosystem according to claim 3, wherein said initial controlcommunications-information in said last time slot (TS) and in saidanother, free, earlier time slot of a subsequent time frame (TF) aretransmitted at a frequency F0.
 5. The protocol for use in an ad-hoc,peer-to-peer radio system according to claim 1, wherein said at leastone time slot (TS) for said control-channel (CC) information istransmitted at a first power level, and said other time slots (TS) forsaid data-channel(DC) information are transmitted at a second powerlevel.
 6. The protocol for use in an ad-hoc, peer-to-peer radio systemaccording to claim 5, wherein said second power level is equal to orless than said first power level, whereby RF interference is reduced. 7.In a protocol for use in a network of terminals each having computermeans, memory means for storing program, and software means therein,said software means of each said terminal comprising means forgenerating communications-information for transmission based on timedivision messaging, said communications-information comprising a seriesof time frames (TM) each divided into a series of time slots (TS); saidcommunications-information comprising at least one time slot in whichcontrol-channel (CC) messaging information is transmitted, and othertime slots in which is transmitted channel data (CD) messaginginformation, the improvement comprising: each said time frame (TF)comprising a last time slot; said software means further comprisingmeans for generating initial control communications-information in arespective said last time slot (LTS) of a respective said time frame(TF) indicating initial presence of a respective said terminal in orderto start communicating with other said terminals.